The present invention generally relates to an excess flow valve that permits fluid flow through a flow line if the flow is below a predetermined flow rate but minimizes the flow if the flow rate rises above the predetermined limit to prevent uncontrolled flow or discharge of fluids.
Excess flow valves are typically used in a capsule to facilitate its installation in various flow lines, fittings, pipe systems, appliances and the like. The excess flow valve acts in response to a high or a low differential pressure between the upstream pressure and downstream pressure of the capsule. In one known configuration, the excess flow valve is comprised of four components including a housing, a seat, a valve plate or body, and a spring or magnet to bias the valve plate. The capsule may be inserted in various flow passageways including a valve body, a connector fitting, a hose fitting, a pipe nipple, a tube, a male iron pipe (MIP), a female iron pipe (FIP), an appliance and other similar installations to provide excess flow protection.
These spring and magnet configurations can be disadvantageous from a cost and assembly perspective due to the number of components. Further, spring operated devices have a tendency to float or close gradually as the internal flow increases right up to the design limit. The tolerances on these designs can have undesirable bypass flow rates when the spring constant changes relative to temperature (primarily on polymeric springs and metal springs in extreme temperatures) and frictional resistance to closing caused by spring buckling on compression springs.